Tweaks workspace animation code per latest from Nicholas. Additionally

ash/wm/workspace/desktop_background_fade_controller.h

Index: ash/wm/workspace/desktop_background_fade_controller.h
diff --git a/ash/wm/workspace/desktop_background_fade_controller.h b/ash/wm/workspace/desktop_background_fade_controller.h
new file mode 100644
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+++ b/ash/wm/workspace/desktop_background_fade_controller.h
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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_WM_WORKSPACE_DESKTOP_BACKGROUND_FADE_CONTROLLER_H_
+#define ASH_WM_WORKSPACE_DESKTOP_BACKGROUND_FADE_CONTROLLER_H_
+
+#include "ash/ash_export.h"
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/compositor/layer_animation_observer.h"
+
+namespace aura {
+class Window;
+}
+
+namespace base {
+class TimeDelta;
+}
+
+namespace ash {
+namespace internal {
+
+class ColoredWindowController;
+
+// DesktopBackgroundFadeController handles fading in or out the desktop. It is
+// used when maximizing or restoring a window. It is implemented as a colored
+// layer whose opacity varies. This results in fading in or out all the windows
+// the DesktopBackgroundFadeController is placed on top of. This is used
+// instead of varying the opacity for two reasons:
+// . The window showing background and the desktop workspace do not have a
+//   common parent that can be animated. This could be fixed, but wouldn't
+//   address the following.
+// . When restoring the window is moved back to the desktop workspace. If we
+//   animated the opacity of the desktop workspace the cross fade would be
+//   effected.
+class ASH_EXPORT DesktopBackgroundFadeController
+    : public ui::ImplicitAnimationObserver {
+ public:
+  // Direction to fade.
+  enum Direction {
+    FADE_IN,
+    FADE_OUT,
+  };
+
+  // Creates a new DesktopBackgroundFadeController. |parent| is the Window to
+//   parent the newly created window to. The newly created window is stacked
+//   directly on top of |position_above|. The window animating the fade is
+//   destroyed as soon as the animation completes.
+  DesktopBackgroundFadeController(aura::Window* parent,
+                                  aura::Window* position_above,
+                                  base::TimeDelta duration,
+                                  Direction direction);
+  virtual ~DesktopBackgroundFadeController();
+
+ private:
+  // ImplicitAnimationObserver overrides:
+  virtual void OnImplicitAnimationsCompleted() OVERRIDE;
+
+  scoped_ptr<ColoredWindowController> window_controller_;
+
+  DISALLOW_COPY_AND_ASSIGN(DesktopBackgroundFadeController);
+};
+
+}  // namespace internal
+}  // namespace ash
+
+#endif  // ASH_WM_WORKSPACE_DESKTOP_BACKGROUND_FADE_CONTROLLER_H_